Electrostatic deflection system



y 0, 1967 L. MANCEBO 3,323,000

ELECTROSTATIC DEFLECTION SYSTEM Filed Jan. 6, 1964 2 Sheets-Sheet l /3 VOLTAGE SOURCE 4 0% l9 22 /2 f/2B+ (/ZA 54 Q68 067 as 64 63 62 61 59 74 7/ 76 (P AC. VOLTAGE A-CVOLTAGE SOURCE SOURCE INVENTOR. LLOYD MA/VCEBO A T TORNE Y 0, 1967 L. MANCEBO 3,323,000

ELECTROSTATIC DEFLECTION SYSTEM Filed Jan. 6, 1964 2 Sheets-Sheet 2 INVENTOR. LLOYD MANCEBO ATTORNEY 3,323,9W' Patented May 30, 1967 ice 3,323,000 ELECTRGSTATIC DEFLECTION SYSTEM Lloyd Mancebo, lLivermore, Calif, assignor to the United States of America as represented by the United States Atomic Energy Commission Filed Jan. 6, 1964, Ser. No. 336,081 13 Claims. (Cl. 31526) The invention described herein was made in the course of, or under, Contract W-7405-ENG-48 with the United States Atomic Energy Commission.

The present invention relates in general to apparatus for electrostatically reflecting charged particles. More particularly, it relates to a closed loop of electrically resistive material having a voltage impressed across points thereon to deflect charged particles passing therethrough.

Generally, electrostatic deflection of charged particles is accomplished by directing the particles between a pair of deflection plates having a difierence of potential therebetween. Moreover, when it has been desired that the deflection system exhibit an influence over two degrees of freedom of particle motion, two pairs of deflection plates have been necessary. Such deflection systems are employed in a variety of beam-deflection tubes.

For example, they are used in multibeam deflection tubes, which deflect various charged particle beams while maintaining their positional relationship to one another. To accomplish this, it is conventional to utilize a spherical electrostatic lens to focus the beams to a common point, the focal point, Where they are simultaneously deflected. Such a spherical electrostatic field has generally been established in one of two ways: either by a charged anode and cathode whose surfaces define segments of concentric spheres; or by a charged cathode, whose surface defines a segment of a sphere, a planar anode, and at least one electrode spacially interposed therebetween, appropriately designed and charged to establish a potential in the region between the anode and cathode which varies inversely as the radial distance from the center of curvature of the cathode surface. To provide the desired deflection for all of the beams, it has been the practice to position the deflection plates at the focal point. Although such a system can provide deflection for all of the beams while their positional relationship remains unaltered, there are disadvantages associated therewith. For example, when it is necessary to control the motion of the beams over two degrees of freedom, the limitations imposed on the physical positioning of the deflection plates result in a poor electrostatic deflection sensitivity. Additionally, the fringing of the electrostatic field beyond the edges of the deflection plates establishes a region where non-linear deflection of the beams occur. Furthermore, as stated before all of the beams are focused at a point, and, ideally, deflection should occur only at this common point. However, as a result of the finite length of the deflection plates in the beam path direction, deflection occurs in regions of convergence and divergence of the beams. Hence, beams following different paths will be deflected different amounts. In order to compensate for this nonlinear deflection, it has been necessary to design deflection systems having a voltage gradient between the deflection plates wihch corrects for it. This invariably requires critical mechanical design and positioning of the deflection plates.

The present invention overcomes the aforementioned imperfections. It is an improved electrostatic deflection system for deflecting a beam of charged particles. More specifically, the invention comprises at least one closed loop of electrically resistive material disposed in the path of the beam to allow passage of the beam through the aperture of the loop. A deflecting voltage is electrically impressed across the loop at opposed locations thereon to establish an electrostatic field transverse to the path of the beam.

In a preferred application of this deflection system to a multibeam deflection tube employing a spherical electrostatic lens, a plurality of electrically resistive rings each having different diameters are disposed between the anode and cathode coaxially along a radius normal to the center of the surface of the cathode. The diameters of the rings vary progressively along the radius noted such that the locus of the inner edges of the series of rings defines a surface which subtends a solid angle substantially identically orientated and substantially equal to that defined by the cathode surface. A deflecting voltage is electrically impressed simultaneously across every ring at diametrically opposed terminals of each to continuously deflect the particle beams while they are in the region between the cathode and anode. The terminals of each ring are identically spacially orientated with those of the other rings.

If it is desired to exercise control over two degrees of freedom of particle motion, an additional pair of diametrically opposite terminals may be disposed on each of the rings, at points angularly displaced from the previously noted terminals. These additional pairs of terminals are electrically connected to a source of deflecting voltage to simultaneously receive a deflecting voltage.

Besides being more rugged and simpler to construct than existing deflection systems, the application of the present invention to the multibeam deflection tube overcomes the previously noted disadvantages. The problem of non-linear deflection is overcome by deflecting the particle beams continuously as they traverse the region between the anode and cathode rather than deflecting the beams at their common point. Furthermore, when it is desired to control the motion of the beams over two dedegrees of freedom, a higher degree of electrostatic deflection sensitivity is obtained by employing the present invention. This results from the circumvention of the limitations imposed on the physical positioning of the deflection plates of conventional deflection systems.

Whereas the multibeam deflection tubes presently known in the art employ what can be termed as a lumped electrode system to form the field of the spherical electrostatic lens, the spaced rings of the present invention affords a means for improving the spherical lens system. This is accomplished by charging each ring to an average voltage which is inversely proportional to its radial position from the center of curvature of the cathode of the tube. This electrode system is designated as a distributed electrode system. As a result of employing such a system, a spherical electrostatic lens field is formed which enables the utilization of a greater total portion of the cathode surface as the emitter.

Accordingly it is an object of the present invention to provide an improved system for electrostically deflecting a beam of charged particles.

More particularly it is an object of the present invention to provide an electrostatic deflection system having improved electrostatic deflection sensitivity characteristics.

It is another object of the present invention to provide an electrostatic deflection system having excellent linear deflection characteristics.

It is a further object of the present invention to provide a source of deflecting. voltage, 13 is I substantially unidirectional an improved electrostatic deflection system for a multidetailed description taken in connection with the accompanying drawing in which:.

FIGURE 1 is a schematic diagram illustrating the operation of the deflection system of the present invention;

FIGURE 2 is anillustration of an improved multibeamdeflection tube employing the deflection system of V the present invention and FIGURE 3 is a schematic diagram illustrating the elec advantages will become more apparent from the following.

.trical circuit connections for operating'a tube of the type shown in FIGURE 2.

FIGURE 1 a ring of electrically resistive material 11 is disposed in the path '12'of 'a'beam of Referring to charged particles. In the absence of an applied deflection voltage to ring II, the beam of charged particles follows an unaltered path 12A.

To provide a de'sir'eddeflection of the particle beam, electrically connected to diametrically opposite locations on ring 11 at terminals 14 and 16. The applied voltageestablishes in the region bounded by ringlllanelectrostatic field 17 which is transverse to the path 12 of the particle established electrostatic field 17 will be slightly curved in those regions close to the surface of ring 11, it will'be in a circular region in which the radius is less than approximately eight-tenths the ring radius. However, the entire electrostatic field region can .be made unidirectional by appropriately grading the resistance around the circumference of the ring such that the voltage dropfrom, for example, terminal 14, to any point 13 on ring 11 corresponds exactly to the voltage drop to a point 19 along the diameter connecting terminals 14 and 16 from which a perpendicular intersects point 18 on ring 11.

The ring 11 is disposed such that the particle beam passes through the substantially unidirectional electrostatic field 17. While in the electrostatic field region, the particle beam is deflected from its original path 12 and emerges from electrostatic field 17 to follow a new path 12B. (Where terminal 14 is positive with respect to terminal 16, FIGURE 1 illustrates the deflection of a beam of negatively charged particles.) Whenever it is desired to exercise control over two degrees of freedom of particle motion, a second source of deflecting voltage (not shown) may be electrically connected to second diametrically opposite locations on ring 11 at terminals 21 and 22. By angularly displacing the second diametrically opposite locations 90 from the previously noted locations, the deflection system will have the characteristics of a rectangular coordinate system. The application of a first deflecting voltage at terminals 14 and 16, and also a second deflecting voltage at terminals 21 and 22, results in establishing in the region bounded by ring 11 a resultant electrostatic field transverse to the path 12 of the particle beam.

Although only a single ring deflection system is illustrated in FIGURE 1, in order to obtain additional deflection, additional rings of electrically resistive material may be disposed along the path traveled by the particle beam. Where a plurality of rings are utilized to deflect a beam of charged particles, the deflecting voltage is simultaneously applied across similarly spacially orientated locations on each ring.

Referring now to FIGURE 2, there is illustrated an improved multibeam deflection tube 23 employing the electrostatic deflection system of the present invention comprising a glass shell 24 having a principal portion approximating a truncated conical surface. A cathode electrode 26 having a surface defined by a segment of a sphere is hermetically secured to the enlarged end 27 of glass shell 24; The conical glass shell 24 and cathode electrode 26 subtend similar solid angles.

Cathode electrode 26'rnay'be of Various types depend- 7 ing upon the intended use of thebeamntube 23. For example, when beam tube 23 is employed as an image tube,

, cathode electrode 26 would'be' a photo-emissive device.

Or, when it is desired to have a cathode ray tube utilizing a multiplicity of electron guns, cathode electrode 26 would be an arrangement of such'a'multiplicity of electron guns.

In order to enhance the ruggedness of tube 23, the I I I truncated end 25 of glass shell 24 is provided with a flared glass extension28, 'An anode electrode 29 defining an aperture 31 is rigidly 28 by a mounting ring 32. Anode electrode 29 is mounted such that its aperture. 31 circumscribes the surface of the solid angle defined by cathode 26.

Cathode electrode 26'and anode electrode 29 are prosecured to the flared extension I I vided with terminals. 33 and 34 respectively. Termi'nals'33 and 34 provide the means of introducing an appropriate I voltage to cathode and anode electrodes 26 and 29 to establish a difference of potential therebetween.

To shape the spherical electrostatic field and provide the means of deflecting the beams of electrons emitted from cathode electrode 26, a plurality of rings of electrically resistive material 39 are disposed between the anode electrode 29' and cathode electrode 26. Preferably, rings 39 are spaced coatings on the inner surface of glass shell 24 subtending a solid angle identically orientated and similar to that defined'by the cathode electrode 26. Each of the rings 39 are provided with a first pair of terminals 41 and 42 diametrically disposed thereon 'and'her I I I rnetically extending through glass shell 24. A secondpair of terminals 43 and 44' are similarly diametrically disposed on each of the rings 39 and hermetically extend I I I through glass shell 24. Preferably the second pair of terminals 43 and 44 areangularly, displaced 90 from the first pair of terminals 41 and 42. Each pair of terminals I I on each ring are longitudinally aligned with the corresponding pair of terminals disposed on the other ring.

In order to better conform the electric field in the region of the flared extension 28 to a spherical configuration, a second truncated conical glass shell 4-6, subtending the same solid angle as the cathode electrode 26, is rigidly secured to the anode electrode 29. The larger end 4 of the second glass shell 46 communicates with the truncated end 25 of the first glass shell 24 and is secured thereto by spring loaded clips 48 and 49. A helical band of electrically resistive material 51 is coated on the inner surface of the second glass shell 46 and electrically communicates the anode electrode 29 with that particular deflection ring juxtaposed the anode electrode 29. The helical band 51 is wound such that the voltage at any point on the helix varies inversely as the radial distance from the center of curvature of the cathode electrode 26.

An electron sensitive display means 36 is disposed to receive those electrons emitted by cathode electrode 26 which pass through aperture 31 of anode electrode 29. Display means 36 may be of various types depending upon the particular application of beam tube 23. For example, a fluorescent screen may be employed whence beam tube 23 is utilized as an image tube or a rastered cathode ray tube. Also, display means 36 may be an arrangement of collector pins when beam tube 23 is utilized as a multiple channel tube.

When focusing is an important requirement, for example, when beam tube 23 is utilized as an image tube, the positioning of display means 36 is critical and must be disposed in accordance with the equation:

whe re S'=the distance between the display means 36 and anode electrode 29, i.e., the image distance, in inches;

D=the diameter of the aperture 31 in inches;

V=the potential difference between the anode electrode 29 and cathode electrode 26 in volts;

E =the electric field on the cathode side of the aperture 31 in volts per inch;

E =the electric field on the display means side of the aperture 31 in volts per inch;

n=the ratio of the radius of curvature of the cathode electrode 26 to the radial distance of the aperture 31 from the center of curvature of the cathode electrode 26;

R =the radial distance of the aperture 31 from the center of curvature of the cathode electrode 26 in inches.

A glass cylindrical housing 37, defining an evacuated region, hermetically communicates display means 36 to the flared extension 28 of glass shell 24.

Whereas previously such multibeam deflection tubes have had a field free region between anode electrode 29 and display means 36, in the improved multibeam deflection tube 23 of the present invention, an electric field may be established in that region by connecting a source of voltage between a terminal 38 of display means 36 and terminal 34 of anode electrode 29.

The establishment of such an electrostatic field is particularly important where the particle beams must be accurately focused at display means 36. Referring to the equation supra, where the region between anode electrode 29 and display means 36 is field free, E is zero and S will have a value to be noted S If, for example, a difference of potential of S kilovolts is established between anode electrode 29 and display means 36, an electric field E of approximately 300 volts per inch is established, with E being much greater than E From the equation supra, it is seen that S will have a value notedas S which is smaller than S Hence by establishing an electric field in the region between the anode electrode 29 and display means 36 one is able to construct a multibeam deflection tube employing a spherical electrostatic lens whose overall length is considerably shorter than those without the electric field.

During the operation of the beam tube 23, there is a tendency for charged particles to collect on the inner surface of the glass shell 24 and glass housing 37. This collection of charges results in distorting the internal electric fields. To collect and conduct away the charged particles, a helical band of electrically resistive material 52 is coated on the inner surface of glass housing 37, and electrically connected between display means 36 and anode electrode 29. Additional helical bands 53 are coated on the inner surface of glass shell 24 electrically interposed the anode electrode 29 and cathode electrode 26 electrically contacting each ring 39 in passing. The resistance per unit length of helical bands 53 should generally be at least an order of magnitude greater than the resistance per unit length of rings 39.

Referring to FIGURE 3, a preferred construction of and electrical circuit connections for operating the multibeam deflection tube will be described. The length of the truncated conical glass shell portion 24 measured along its surface between the larger end 27 and the truncated end 25 is 5% inches. The diameter of the larger end is 5 inches. The diameter of the truncated end is 1% inches. The radius of curvature of the surface of cathode electrode 26 is 9 inches. The length of conical glass shell 46 measured along its surface is 2% inches, with its larger end having a diameter of 1% inches and its truncated end '4; inch. The length of the cylindrical housing 37 is 14 inches and its diameter 5 inches.

The rings 39 are one mil coatings, inch wide and are spaced at inch intervals between the enlarged end 27 and truncated end 25 of glass shell 24. The uniform resistance per mil length of rings 39 is 10 kilo-ohms.

The helical windings 51, 52 and 53 have a resistance per mil length of 100 kilo-ohms.

In operation, cathode electrode 26 is electrically connected to a negative terminal 54 of a DC. voltage source 56. A positive terminal 57 of source 56 is electrically connected to anode electrode 29. A resistance voltage divider comprised of resistors 58, 59, 61, 62, 63, 64, 66, 67 and 68 is electrically connected serially between terminals 54 and 57 of source 56. Each ring 39 is electrically connected to a common junction of successive serially connected resistors. The values of the serially connected resistors are selected such that the potential in the region between anode electrode 29 and cathode electrode 26 varies inversely as the radial distance from the center of curvature of the cathode electrode 26.

Display means 36 is electrically connected to source 56 at a second positive terminal 69 which is positive with respect to terminal 57. The potential difference between anode electrode 29 and display means 36 provides a post acceleration region for those electrons emitted by cathode electrode 26 and passing through aperture 31.

To provide means for deflecting the electrons emitted by cathode electrode 26 in a first ordinate direction, a first A.C. voltage source 71 is A.C. connected to diametrically opposite locations on all the rings 39, the diametrically opposite locations on the rings being longitudinally aligned. The A.C. voltage source 71 may be, for example, a sinusoidal varying voltage, a pulse varying voltage, a ramp function or other A.C. type voltage sources depending upon the particular application of the multibeam tube.

The aforementioned A.C. connection is accomplished by electrically connecting a capacitor 72 between successive aligned locations thereby forming a capacitive divider network associated with diametrically opposite aligned locations. Source 71 is electrically connected to each divider network at their respective terminals '73 and 74.

To deflect the beams of electrons in a second ordinate direction angularly displaced 90 from the first direction, a second A.C. voltage source 76 is similarly connected to second diametrically opposite locations on rings 39 angularly displaced 90 from the first diametrically opposite locations.

The component values of the resistors and capacitors are listed infra:

A multibeam deflection tube constructed and electrically connected as hereinbefore described was utilized as an image tube, with cathode electrode 26 being a photoemissive device and display means 36 a fluorescent screen. Of the 5 inch diameter cathode, 80% of its surface was usable as the emitter. Furthermore, an image of high resolution was reproduced on the fluorescent screen whose position on the screen was controlled by the application of pulses of voltage simultaneously across the deflection rings 39.

While the present invention has been hereinbefore described with respect to particular applications of a preferred embodiment, numerous modifications and variations are possible without departing from the scope of the invention. For example, the improved multibeam deflection tube may be utilized to provide a multiple image display by approximately time sequentially applying the deflection voltage to the rings of the deflection system. Hence, the scope of the invention is to be limited only by the terms of the following claims.

What is claimed is:

1. In a multibeam deflection tube including a spherical electrostatic lens having a cathode means and anode, said cathode means disposed to define a surface segment of a sphere, an improved electrostatic deflection system for deflecting beams of charged particles comprising in combination with said spherical electrostatic lens,

(A) a plurality of spaced rings of electrically resistive material disposed between said anode and cathode means coaxially along a radius normal to the center of the surface of said cathode means, each of said rings having a different diameter, said rings disposed progressively along said radius such that the locus of the inner edges of the series of rings defines a surface which subtends a solid angle substantially identically orientated and substantially equal to that defined by said cathode means, and

(B) means for impressing a respective voltage simultaneously across diametrically opposite locations on each of said rings thereby establishing a substantially unidirectional electrostatic field transverse to the path of said beam in the regions bounded by said rings, said diametrically opposite locations on each ring being longitudinally aligned with their corresponding diametrically opposite locations on the other rings.

2. In a multibeam deflection tube including a spherical electrostatic lens having a cathode means and anode, said cathode means disposed to define a surface segment of a sphere, an improved electrostatic deflection system for deflecting beams of charged particles comprising in combination with said spherical electrostatic lens,

(A) a plurality of spaced rings of electrically resistive material disposed between said anode and cathode means coaxially along a radius normal to the center of the surface of said cathode means, each of said rings having a different diameter, said rings disposed progressively along said radius such that the locus of the inner edges of the series of rings defines a surface which subtends a solid angle substantially identically oriented and substantially equal to that defined by said cathode means,

B. Means for charging the entirety of each of said rings to an average voltage potential which is inversely proportional to its radial position from the center curvature of said cathode means, thereby establishing a potential gradient between said cathode means and anode which varies inversely with the radial distance from the center of curvature of said cathode means,

(C) a first means for impressing a respective voltage simultaneously across first diametrically opposite locations on each of said rings, and

(D) a second means for impressing a respective voltage simultaneously across second diametrically opposite locations on each of said rings thereby establishing in addition to said potential gradient a substantially unidirectional resultant electrostatic field transverse to the path of said beams in the regions bounded by said rings, said diametrically opposite locations on each ring being longitudinally aligned with those diametrically opposite locations on the other rings arranged to receive a simultaneous voltage, said first diametrically opposite locations angularly displaced from said second diametrically opposite locations.

3. A multibeam deflection tube comprising,

(A) a truncated conical shell of insulating material defining an evacuated region,

(B) a cathode electrode having a surface defined by a segment of a sphere, said cathode hermetically secured to the larger end of said conical shell to subtend a solid angle substantially identically oriented to that subtended by said conical shell,

(C) an apertured anode electrode secured to the truncated end of said conical shell, the aperture of said anode circumscribing the surface of the solid angle defined by said cathode,

(D) an electron sensitive display means disposed to receive those electrons emitted from said cathode which pass through said apertured anode,

(E) a housing of insulating material defining an evacuated region hermetic-ally communicating said display means with said truncated end of said conical shell,

(F) a plurality of spaced rings of electrically resistive material disposed between said anode and cathode coaxially along a radius normal to the center of the surface of said cathode, each of said rings having a different diameter, said rings disposed progressively along said radius such that the locus of the inner edges of the series of rings defines a surface which subtends a solid angle substantially identically orientated and equal to that defined by said cathode,

(G) means adapted to establish a continuous potential drop from said anode to said cathode, said potential in the region between said anode and cathode varying inversely as the radial distance from the center of curvature of said cathode,

(H) means for impressing a respective voltage simultaneously across diametrically opposite locations on each of said rings thereby establishing in the regions bounded by said rings a substantially unidirectional electrostatic field transverse to the path of the beams of electrons emitted by said cathode, and

(1) means adapted to establish a continuous decrease in potential from said display means to said anode.

4. In a multibeam deflection tube as recited in claim 3 further defined by said display means being disposed at a distance from said anode defined by the equation:

i 1 S' g1 4V 2(nl) 1.- E E n2 where:

S=the distance between the display means and the anode in inches, D=the diameter of the aperture in inches, V=the potential difierence between the anode electrode and the cathode electrode in volts, E =the electric field on the cathode side of the aperture in volts per inch, E ==the electric field on the display means side of the aperture in volts per inch, n=the ratio of the radius of curvature of the cathode to the radial distance of the aperture from the center of curvature of the cathode, R =the radial distance of the aperture from the center of curvature of the cathode in inches.

. S. In a multibeam deflection tube as recited in claim 3 further defined by said diametrically opposite locations on each ring being longitudinally aligned with their corresponding locations on the other rings.

6. In a multibeam deflection tube as recited in claim 3 further defined by said first and second locations on each ring being angularly displaced with respect to one another.

7. In a multibeam deflection tube as recited in claim 3 further defined by,

(A) a first helical band of electrically resistive material electrically interposed said display screen and said anode, said helical band disposed on the inner surface of said housing, and

(B) additional helical bands of electrically resistive material electrically interposed said anode and said cathode electrically contacting each of said rings, said helical bands disposed on the inner surface of said conical shell, the resistance per unit length of said helical bands being at least an order of magnitude greater than the resistance per unit length of said rings.

8. In a multibeam deflection tube as recited in claim 3 further defined by each of said rings being a continuous coating of electrically resistive material on the inner surface of said conical shell.

9. A multibeam deflection tube comprising,

(A) a truncated conical shell of insulating material defining an evacuated region,

(B) a cathode electrode having a surface defined by a segment of a sphere, said cathode hermetically secured to the larger end of said conical shell to subtend a solid angle substantially identically orientated to that subtend by said conical shell,

(C) an apertured anode electrode secured to the truncated end of said conical shell, the aperture of said anode circumscribing the surface of the solid angle defined by said cathode,

(D) an electron sensitive display means disposed to receive those electrons emitted from said cathode which pass through said apertured anode,

(E) a housing of insulating material defining an evacuated region hermetically communicating said display means with said truncated end of said conical shell,

(F) a plurality of spaced rings of electrically resistive material disposed between said anode and cathode coaxially along a radius normal to the center of the surface of said cathode, each of said rings having a different diameter, said rings disposed progressively along said radius such that the locus of the inner edges of the series of rings defines a surface which subtends a solid angle substantially identically orientated and substantially equal to that defined by said cathode,

(G) means adapted to establish a continuous potential drop from said anode to said cathode, the potential in the region between said anode and cathode varying inversely as the radial distance from the center of curvature of said cathode,

(H) a first means for impressing a respective voltage simultaneously across first diametrically opposite locations on said rings,

(I) a second means for impressing a respective voltage simultaneously across second diametrically opposite locations on said rings thereby establishing in the regions bounded by said rings a substantially unidirectional resultant electrostatic field transverse to the path of the beams of electrons emitted by said cathode, said diametrically opposite locations on each ring being longitudinally aligned with their corresponding locations on the other rings arranged to receive the same simultaneous voltage, said first diametric-ally opposite locations angularly displaced from said second diametrically opposite locations,

(1) means for establishing a continuous decrease in potential from said display screen to said anode.

10. In a multibeam deflection tube as recited in claim 9 further defined by said first and second locations on each ring being angularly displaced 90 with respect to one another.

11. In a multibeam deflection tube as recited in claim 9 further defined by,

(A) a first helical band of electrically resistive material electrically interposed said display screen and said anode, said helical band being disposed on the inner surface of said housing, and

(B) additional helical bands of electrically resistive material electrically interposed said anode and said cathode electrically contacting each of said rings, said helical bands being disposed on the inner surface of said conical shell, the resistance per unit length of said first and additional helical bands being at least an order of magnitude greater than the resistance of said rings.

12. In a multibeam deflection tube as recited in claim 9 further defined by each of said rings being a continuous coating of electrically resistive material on the inner surface of said conical shell.

13. A multibeam deflection tube comprising,

(A) a first truncated conical glass shell defining an evacuated region, the truncated end of said conical shell having a flared extension,

(B) an electron emis-sive cathode electrode having a surface defining a segment of a sphere, said cathode hermetically secured to the larger end of said conical shell to subtend a solid angle substantially identically orientated to that subtended by said conical shell,

(C) a second truncated conical glass shell substantially smaller than said first conical shell, the larger end of said second conical shell communicating with the truncated end of said first conical shell to form a resultant truncated conical shell,

(D) an apertured anode electrode, said anode rigidly secured to the truncated end of said second glass shell, the aperture of said anode circumscribing the surface of the solid angle defined by said cathode,

(E) insulating mounting means rigidly securing the flared extension of said first conical shell to said anode,

(F) an electron sensitive display means disposed to receive those electrons emitted from said cathode which pass through said apertured anode,

(G) a glass cylindrical housing defining an evacuated region hermetically communicating said display means with the flared extension of said first conical shell,

(H) a plurality of spaced rings disposed between the cathode and the truncated end of said first conical shell, each of said rings being a continuous coating of electrically resistive material on the inner surface of said first conical shell,

(I) a first means for impressing a respective voltage simultaneously across first diametrically opposite 1ocations on said rings,

(J) a second means for impressing a respective voltage simultaneously across second diametrically opposite locations on said rings thereby establishing in the regions bounded by said rings a substantially unidirectional resultant electrostatic field transverse to the path of the beams of electrons emitted by said cathode, said diametrically opposite locations on each ring being longitudinally aligned with their corresponding locations on the other rings arranged to receive a simultaneous voltage, said first diametrically opposite locations angularly displaced from said second diametrically opposite locations,

(K) a first helical band of electrically resistive material coated on the inner surface of said housing and electrically connected between said display screen and said anode,

(L) a second helical band of electrically resistive material coated on the inner surface of said second conical shell and electrically connected between said anode and said ring juxtaposed said anode,

(M) additional helical bands of electrically resistive material coated on the inner surface of said first conical shell between said rings, each of said addi- 1 l l 2 tional helical bands electrically connected between References Cited said juxtaposed rings, the resistance per unit length UNITED STATES PATENTS,

of said helical bands being at least an order of magnitude greater than the resistance of said rings, 2179097 11/1939 313'-78 (N) means adapted to establish ad-ifference of potential 5 g; I I

in the region between said anode and said cathode inversely as the radial distance from the center of a Curvature of said cathode, and JOHN W. CALDWELL, Acting Przmaly Exammer. (0) means adapted to establish a continuous decrease T. A. GALLAGHER, R. K. ECKERT, JR.,

in potential from said display screen to said anode. 10 Assistant Examiners. 

1. IN A MULTIBEAM DEFLECTION TUBE INCLUDING A SPHERICAL ELECTROSTATIC LENS HAVING A CATHODE MEANS AND ANODE, SAID CATHODE MEANS DISPOSED TO DEFINE A SURFACE SEGMENT OF A SPHERE, AN IMPROVED ELECTROSTATIC DEFLECTION SYSTEM FOR DEFLECTING BEAMS OF CHARGED PARTICLES COMPRISING IN COMBINATION WITH SAID SPHERICAL ELECTROSTATIC LENS, (A) A PLURALITY OF SPACED RINGS OF ELECTRICALLY RESISTIVE MATERIAL DISPOSED BETWEEN SAID ANODE AND CATHODE MEANS COAXIALLY ALONG A RADIUS NORMAL TO THE CENTER OF THE SURFACE OF SAID CATHODE, MEANS, EACH OF SAID RINGS HAVING A DIFFERENT DIAMETER; SAID RINGS DISPOSED PROGRESSIVELY ALONG SAID RADIUS SUCH THAT THE LOCUS OF THE INNER EDGES OF THE SERIES OF RINGS DEFINES A SURFACE WHICH SUBTENDS A SOLID ANGLE SUBSTANTIALLY IDENTICALLY ORIENTATED AND SUBSTANTIALLY EQUAL TO THAT DEFINED BY SAID CATHODE MEANS, AND (B) MEANS FOR IMPRESSING A RESPECTIVE VOLTAGE SIMULTANEOUSLY ACROSS DIAMETRICALLY OPPOSITE LOCATIONS ON EACH OF SAID RINGS THEREBY ESTABLISHING A SUBSTANTICALLY UNIDIRECTIONAL ELECTROSTATIC FIELD TRANSVERSE TO THE PATH OF SAID BEAMS IN THE REGIONS BOUNDED BY SAID RINGS, SAID DIAMETRICALLY O PPOSITE LOCATIONS ON EACH RING BEING LONGITUDINALLY ALIGNED WITH THEIR COR- 